Process for removing acids from hydrocarbons



Patented Dec. 5, 1944 PROCESS FOR REMOVING ACIDS FROM HYDROCARBONS OrrisL. Davis and Alan C. Nixon,'0akland, Calif,, assignors toShelLDevelopmentCompany, San .Francisco, Calif., a. corporation ofDelaware No Drawing. Application July'l7,i19"42, Serial-No. 451,376

16 Claims.

This invention deals with an improvement in processes for extractingweak'acids from hydrocarbons. Moreparticularly, it is concerned with amethod for improving the rate of separationof alkaline extractingsolutions from gasolines or for fac'ilitating steam stripping theresulting spent alkalinesolution, ifthe-latt'eris desired, or both.

It is known that gasolines frequently contain weak-acids such as thosehaving dissociation constants below about e. g. HzS, mercaptans, alkylphenols, etc.,'which acidsmustgbe removed for various reasons. A numberof processes have been developed for extracting these acids. All ofthese (processes have in common the step of treatingthe hydrocarbon oilcontaining theacid with an alkaline solution, and thereafter separatingthe hydrocarbon oil'from'the resulting alkaline solution containingsalts of the absorbed acid. For reasonsof economy, the resulting spentalkaline solution is usually regenerated, steam stripping in "generalbeing'the preferred method of regeneration. The regenerated solution isthen used for the extraction of further quantities of :acids fromhydrocarbons containing them.

*Examples of particular processes for the extraction of weak acidsnormally associatedwith petroleum oils are: processes involving theextraction 'of H28 from gaseous 'or liquid hydrocarbonsbyuse of aqueous.solutions of tripotassium phosphate, sodium phenolate, sodium borate,sodium or potassium carbonate, organic bases such as ethanolamine,diamino ,propanol, piperidine, etc. processes involving the extractionof a1- kyl phenols from hydrocarbon distillates with solutions of alkalimetal hydroxides, preferably having concentrations of about 25-50%; andprocesses involving the extraction of mercaptans with so-calledsolutizer solutions by the solutizer process, etc.

In 'the solutizer process, a sour gasoline distillate containingmercaptans is extracted with an aqueous caustic alkali solutioncontaining one or several solutizers or solubility promoters formercaptans. Suitable solutizers are, for example, alcohols such asmethanol, ethanol, propanol, etc. aliphatic alkanolamines and aminoalkyl amines in which "the alkyl radicals contain 2 or 3 carbon atoms;diamino alcohols, glycols and amino glycols of 3 to 5 carbon atoms;alkyl glycerinesin which the total number of "carbon atoms in the alkylradicals is from :1 to 4; monomethyl glyceryl ether; diamino, dihydroxyor 'aminohydroxy alkyl ethers or thioethers in which the alkyl radicalshave from "2 to 3 carbon atoms;

alkali metal salts of fatty acids having from '3 to5 carbonatoms;-or,inthe case of potassium salts, having from l 1106 carbon atoms; amino orhydroxy fatty acids having-from2 to 7 carbon atoms, *phenyl acetic acid,hydroxy or amino phenyl aoetic'acid, alkyl phenols,etc.

It is known that among the many solutizers whichare'employed topromotesolubility of mercaptans in'strong'ly alkaline aqueous solutions, thealkali metal 'alkyl phenolates aid in the production of sweet gasolines,of reasonable oxidation stabilities. This phenomenon, which has beendescribed in the Yabrofi-White Patent 2,-223379835 due to the'fact thatwhile mercaptans are extracted fromthe sourgasoline substantiallycompletely, natural gum inhibitors, i. 'e. alkyl phenols normallycontained in the gasolines, are only partially extracted, an alkylphenol equilibrium being established between the gasoline and theextracting solution. Therefore, it is very often-advantageousto employfor the extraction a solutizer solution to which a certain amount ofalkyl "phenolates is added. Many gasolines, and more particularly almostall cracked gasolines, contain "alkyl phenols, at least a portion ofwhich will accumulate in the solutizer solution. Inasmuch as thesolutizer solution is continuously circulated'from an extracting stageto asteam regeneration stage and back to the extraction stagegeventraces of alkylphenols contained inthe gasoline will eventually build upin thesolutizer solution until the concentration of thealkyl \phenolatein the solutizer solution is inequilibrium with the'concentration of thealkylphenolsin theincoming gasoline. It has been found that in spite ofthorough caustic alkali pretreatment, the incoming gasoline may containenough alkyl phenols to establish over 'an extended period of operationan equilibrium 'concentration-ofanywhere between about 3 and 20% alkylphenolates in the solutizer solution, even though the original treatingsolution may have been free from phenolates.

Aqueous solutions containing substantial amounts of alkyl phenolates arenot advantageous becausethey have a tendency to form emulsions whichseparate slowly. It hasbeen found in the past that in order to avoidemulsion troubles the concentration of the alkyl phenolates must be'keptbelow certainlimits, otherwise more or less permanent emulsions may form(U. S. Patent 2,202,039)

It has further been found that alkaline solutions which are used forextracting weak acids from hydrocarbon oils of the gasoline range asdescribed above and which are thereafter regenerated by steam stripping,may gradually accumulate substances which act as emulsifiers and foaminducers. In general, processes dealing with the removal of H25 aretroubled primarily with foaming, whereas the processes dealing with theextraction of mercaptans, phenols, etc., frequently are subject not onlyto foaming, but also to the formation of stubborn emulsions which reducethe rate of separation.

As a result, maximum throughput through an extraction unit of a givensize may be greatly reduced, or else the use of large settlers or ofcentrifuges may be required. Likewise, the capacity of steam strippersmay be greatly curtailed.

The nature of the substances responsible for foaming and emulsiondifficulties is not definitely salts preferred are those which are freefrom carboxyl radicals, contain at least carbon atoms per molecule, andhave a molecular weight below about 1000. Such salts have been foundparticularly effective in the breaking of emulsions which may formbetween gasolines and the treatprealkali in a normality of at leastabout 2 and, in

addition, containing substantial amounts (e. g. normally %"or more) ofthe solutizer or solutizers suchias alkali metal phenolates and other 1solutizers described above.

established. It may be that a substance is inb volved which is relatedto the gums that form in .gasolines due to oxidation or it maybe due toresinous. materials formed as by interaction of some of the componentsof the gasolines (possibly impurities) with the alkaline treatingsolution or acomponent thereof. For example, it is quite possible thatin .the case of solutizer treatment with solutions containingphenolates, a phenol type resin is formed, for instance by interactionwith mercaptans, aldehydes or other impurities. Such a possibility issupported by the fact that solutizer solutions containing phenolateshave in the past given the greatest difficulties.

Accordingly it is a purpose of this invention to provide means forimproving the rate of separation of aqueous alkaline treating solutionsfrom gasolines which are being treated. Another purpose is to reduce thefoaming which occurs during regeneration of the treating, solutions bysteam stripping. invention is to provide means for preventing theformation of emulsions caused by the presence of accumulated emulsifiersin solutizer solutions, particularly in those containing alkylphenolates; and it is yet another purpose to break emulsions formed bygasolines in solutizer solutions.

This invention comprises maintaining in an aqueous alkaline treatingsolution small amounts of two substances:' (1) a water-soluble surfaceactive alkali metal salt of an organic sulfonic or sulfate ester acid;and (2) a mineral oil, which combination is added to reduceemulsification and foaming between gasolines and the solution. The termsurface active as herein used refers to the ability of the salt toreduce materially the surface tension of pure water when added theretoin small amounts, that is, in amounts of a few tenths of one percent.The term water-soluble is not limited to substances which form truesolutions but includes substances which spontaneously form colloidalsolutions or dispersions as well. I

In order thatv these two substances which are added to the aqueousalkaline treating solution may be more or less permanently useful in aregenerative process wherein said solution is continuously regeneratedandfrecirculated for further extracting gasolines' containing weakacids, it is desirable that these substances have a number of definiteproperties. The required properties of the surface active salts (1) willbe discussed first. I

The types of organic sulfonic and sulfate ester. acids which producethese surface active salts,

as wellas their methods of manufacture, aregen- Still another purpose ofthis.

Further, the active salts should not be extracted from the solutizersolution when the latter is in contact with the gasolines. The presenceof alkali metalsalts of sulfonic or sulfate acids in gasolineadverselyaffects many of its properties, e. g. its stability, A. S. T. M. gum,copper dish gum, color, etc. Therefore it is desirable that the salts besubstantially insoluble in hydrocarbon oils, after being wetted bywater, although they may be and often are soluble or colloidallydispersable in hydrocarbons when wetted by the latter.

. Furthermore, the salts should be reasonably air through the packingglands, and this air is then dissolved in the on being pumped.v

.In'scme few instances, it may become desirable to remove the surfaceactive salt from the extracting solution, in which case it should have aproperty which makes possible such separation. In"most instances theremoval can be accomplished relatively easily by adding small amounts oflime water or other hydroxide or water-soluble saltof a pclyvalent metalto the extracting solution, polyvalent metal salts and particularly thecalcium salts of most organic sulfonates and sulfates of this inventionbeing insoluble in the solutizer'or similar extracting solutions andbeing precipitated as a curd which can be settled or filtered out.

Of the two classes of surface active compounds suitable for the purposeof this invention, i. e. the alkali metal salts of sulfonic acids andsulfate ester acids, the former are preferred as being in general moreresistant to hydrolysis. Resistance to hydrolysis in the presence offree caustic alkali and under the conditions .of' steam regeneration isan important property when it is desired that the efiect of the surfaceactive salts be more or less permanent.

Suitable sulfonates and sulfates may, if desired, contain non-functionalradicals such as halogen, hydroxyl, ether, amino, imino, hydrosulfide,sulfide, carboxyl ester, etc., radicals.

Specific sulfonates which we have found to be manufacture of medicinaloils by acid treatment;

the products of. treating: kerosene or lube oil, ex-- tracts withconcentrated sulfuric acid; various aliphatic or alicyclic sulfonicacids such as fatty sulfonic acids, fatty aromatic sulfonic acids,naphthene sulfonic acids; sulfonic acids of variousaromaticthydrocarbons, such as various alkylated benzenes, diphenyls,xylenes, diphenyl methanes, naphthalenes, anthracenes, phenanthrenes,tetralines, alkyl phenols such as those contained in cracked petroleumdistillates, alkylated chlornaphthalenes, naphthylamines, diphenyloxides, chlorinated diphenyl oxides, sul-, fides or amines; alkylatedpyridines, quinolines, isoquinolines, pyrrols, pyrrolidines, piperidine,thiophenes, thiophanes, etc. or various sulfonic acids of carboxylicacid esters or amides, such as the ester sulfo-carboxylic acids orsulfonato amides having the general formulae:

RSO2,M

ORSO3M o=o-R' respectively, wherein the R radicals are organic radicals,such as aliphatic or cyclic hydrocarbon radicals, M is an alkali metaland n. is an in- 1 tegar normally not greater than 2.

.'While the carboxylic acid esters and amides listed above are veryeffective herein, many of them have the disadvantage of beingsusceptible to hydrolysis during steam regeneration of the solutizersolution forming free carboxylic acids upon decomposition, .the salts ofwhich are likely to cause foaming. a

The alkali metal salts of sulfonic acids possessing at least one alkylradical are in general far more effective than the salts ofcorresponding sulfonic acids not possessing them. For example, thealkali metal salts of naphthalene or anthracene sulfonic acids are onlymildly beneficial, whereas the corresponding salts of, for example,monoor dibutyl naphthalene sulfonic acids or of retene sulfonic acid arehighly effective.

The sulfonates may be prepared in various ways. Aromatic sulfonates aremost readily obtained by simply treating aromatic compounds withconcentrated or fuming'sulfuric acid. Aliphatic sulfonates may beobtained under some conditions by treating olefines or diolefines withconcentrated sulfuric acid, or by treating organic acid sulfates withsodium sulfite so as to eliminate sodium sulfate, or by oxidation ofmercaptans with nitric acid, etc. Satisfactory sulfonates may also beobtained by treating a lubricating oil with concentrated or fumingsulfuric acid.

Sulfate ester acids of which the alkali salts are suitable herein are,for example: the fatty sulfates, such as mono lauryl, cetyl,'steary1,etc., sulfateacids; mono esters of sulfuric acid obtained by treatingwith concentrated to moderately concentrated sulfuric acid variousolefines or alcohols such as the long chain olefines obtained in thevapor phase cracking of wax at about 1020-1040 F., polymers obtained inthe polymerization of normally gaseous olefines with inorganic polyoxyacids or Friedel-Crafts catalysts, fatty, or naphthenic alcoholsobtained in the catalytic reduction of fatty or naphthenic acids,alcohols obtained by condensation of ketones or aseaasa aldehydesfollowed by, ahydrogenatiom oralkyl 75 ters of degree.

aromatic mono esters of sulfuric acid, etc. A convenient source for manyof the active sulfate ester acids is the sludges obtained in the acidtreatment of cracked distillates, or the spent acids obtained in thepolymerization of olefines,

or in the alkylation of isoparaffins with olefines with sulfuric acid.

The amounts of surface active salts which must. be added to increase therate of separation of the I emulsion are generally quite small and varyfrom tion greatly enhances the solvent power for the salts. Preferablythe amount added should not exceed its solubility limit in aqueoussolution. However, within reasonable limits, the amount of saltnecessary is directly proportional to the amount of emulsifiers presentin the solution.

It is desirable that the beneficial effect of the salt shall not berestricted to and be dependent on a specific range of concentrationsubstantially narrower than the limits indicated abovethat is to say,there should not be a sudden reversal of the beneficial effect, i. e. anincrease in the emulsification tendencies of the extracting solutionupon addition of a slight excess of the salt over the optimum quantity.On the contrary,

the beneficial elfects should extend over substantially the entire rangeof concentration indicated, and changes in the eifects due to deviationsfrom the optimum concentration should be only mat- Many surface activesalts, particularly, the ordinary soaps such as sodium stearate, sodiumoleate, etc., while efiecting deemulsification in certain specificamounts, when present in slightly larger amounts increase rather thandecrease the emulsion tendencies of the extracting solution. Forexample, sodium stearate in a concentration of .06% effectively broke asemi-stable solutizer emulsion, while in a .08% concentration a stableemulsion remained.

It is, however, understood that the beneficial effects of the surfaceactive salts of this invention do not extend to all concentrationsthereof. When present in excessive amounts, e, g. in amountssubstantially above about 1%, even the best of the active compounds mayact as emu1- sifiers, rather than as settling accelerators or emulsionbreakers or both. For this reason it is important that the concentrationof the demulsifyingagents in the aqueous alkaline solution be limited towithin the approximate useful limits indicated.

For the same reason it is essential that the.

' kali.

The properties of the second of these additive substancesthe mineraloils (2)-will now be discussed in detail.

It has been found that in the absence of surface active salts ofsulfonic and sulfate ester acids, heavy aromatic oils, e. g. thosehaving high boiling ranges, are the best defoaming agents. However, theyare not satisfactory in systems involving the treatment of hydrocarbonoils of the gasoline range, because if even very small In general, the

amounts of such oils are extracted by the gasoline they willdetrimentally increase the gum content of the gasoline. This detrimentaleffect is also characteristic of other heavy oils, including heavyparafiinic oils, although only the arcmatic oils have any appreciabledefoaming'properties. by themselves. The lighter the oil added the moreeasily it is lost by extraction and/or stripped out during steamregeneration. Relatively light aromatic oils in the gas oil range whichdo not give detrimental gum in gasoline due to the small amountsextracted by the gasoline are not so effective as defoaming agents asare the heavier aromatic oils. Although such light aromatic oils aloneare better defoamers than the'light parafiinic oils the former have thedisadvantage of frequently causing fluorescence.

Paraffinic oils by themselves are ineffective as defoamersand often actas pro-foamers; however, in combination with the surface active salts ofthe type previously described they have the unexpected property of verygreatly improving the defoaming properties of these salts. This propertyis also true for light aromatic oils but not to such a noticeableextent. matic oils should not be used if fluorescence in the treatedgasoline is undesirable.

Therefore, it is important to obtain an oil which is light enough not tocause undesirable gum content in the gasoline, but yet heavy enough notto be too easily lost in the stripper. Suitable light oils should befree from asphalts, resin, and gum-forming impurities, and must possessboiling ranges between about 400 and about 900 R, preferably betweenabout 500 and about 750 F. Their viscosities may range between about 30and 200 Saybolt Universal seconds at 100 R, preferred viscosities beingbetween about 40' and '70 seconds at 100 F. Because of generalundesirability of fluorescence it is preferred to employ paraffin oilshaving aniline points above about 122 F., and a specific dispersionbelow about 150 as determined by a method disclosed in an. article byVon Fuchs and Andersen in Industrial and Engineering Chemistry, vol. 29,No. 3, March 1937, .pp. 319-325.

There are still other properties which these oils must possess: theymust be readily dispersible ineffective amounts in the aqueous treatingor extracting solution, so that the maximum effect may be obtained, andthey should be reasonably stable toward the action of small amounts ofoxygen, in the presence of strong caustic at the elevated temperaturesemployed in the regeneration step.

Some specific types. of oils whichmay be used and which have the aboverequired properties are: gas oil, light'lubricating oil, spray oil, andother extracted oils which have been extracted "by such selectivesolvents as liquid S02, nitrobenzene, nitro-toluene, furfural, acetone,aniline, lpheno-l, cresylic acids, dichlordiethyl ether, SO2- benzenemixtures, other selective solvents, or combinations of solvents above,and anti-solvents such as ethane, propane, butane, petroleum ether,etc., as well as some lower boiling extracts.

The amounts of these oils which must be added to reduce the foaming andimprove the rate of separation of the treating solution and thehydrocarbon oil vary from about .001% to about 2% by weight, generallyabout .1 of the treating solution. Within reasonable limits, the amountof oil necessary is directly proportional tothe amount of foaming agentspresent in the However, aroit may be necessary from time to time in acon-- tinuous process, 1. e. every10- or 15 cycles of the treatingsolution, to add small amounts of oil to maintain the concentration inthe treating solution within the desired limits to effect efiicientdefoaming, because small quantities of the oil are lost due toextraction by the gasoline treated. If desired, this addition may becontinuous As indicated before, the surface active sulfates orsulfonates used in the treatment must be wetted by the aqueous solution,rather than by the hydrocarbons. It has been found that if the agent isfirst dissolved or dispersed in the gasoline, only a portion will beretained by the aqueous solution upon contact under ordinary extractionconditions, the remainder staying in the gasoline phase. On theotherhand, if the agent is first dissolved or thoroughly dispersed inthe aqueous solution, it'is not usually extracted by the gasolines toany extent under normal extracting conditions.

generative process such as the solutizer process, 1 it is convenient toaddthe active salt and mineral oil, or preferably its slurry in,- water,to the spent extracting solution emanating from the extractor. Thissolution is then heated and thoroughly agitated in thev steam stripperin the course of the regeneration step, whereby the desired dispersionor dissolution is achieved.

While in the foregoing the invention has been described as applyingparticularly to regenerative processes such as the sweetening of sourgasolines by the solutizer process, it is also applicable to theextraction of alkyl phenols, etc., from hydrocarbon oils by processesnot calling for regeneration such as those described in U. S. Patents2,134,390 and 2,213,596. In these processes, alkyl phenols are extractedfrom clistillates containing them with strong caustic soda (25-50%concentration) to result in an extract of high alkyl phenolate content.This extract separates slowly from the distillate, frequently more thana day being required to obtain complete separation. The addition ofrequisit amounts of a surface active salt of this invention materiallyreduces the settling time, often causing a complete sepa-- ration in afew minutes. In the table below, effects of a number of representativesurface active salts and mineral oils covered by this invention areshown. To evaluate their performance samples of a solutizer solutionhaving the-following composition were subjected to an emulsion and afoaming a molecularweig ht below about 1000, and said test inwhic'h'theyjwere" mixed with a cracked gasoline under conditions similar tothose which would be encountered in thesolutizer process. The emulsiontest was carried" out by stirring a ml. sample of solutizer solutionwith 25 ml. of a cracked gasoline for 5 minutes'in a 6" x 1" test tubeat a stirrer speed of approximately 2900 R. P. M., and then measuringthe time necessary for the solutizer solution to separate 'from thegasoline. The foaming test was carried out by heating a ml; sample ofsolutizer solution diluted with 5 ml. of water ina 32 x 600 mm. testtube with two carborundum boiling chips (6 mesh) at such arate thatboiling starts in 3 minutes :5 seconds. The maximum height reached bythe solution and foam after boiling starts in the foam rating. i Theresults of these tests were as follows: v i I 7 Tube foam rating 5Sample 1 Surface active alkali setthn metal salt Without With time oiloil 1 None 8. 5 7. 2 Alkylnaphthene sullonate- 8.25 6.625 3 Long-chainalcohol sulfate. 8 6 4 Alkyl aryl sulfonate 8.125 3.875 5 Sulfonatedalkyl hvdrou. 7. 25 5.375 6. 625 6. l 7 do 6. 25 4 3 8 Sodium petroleumsulfon' ate -4 5175 3.75 i 3 The total amount of additive surface activesalt and/or oil for each test was .1 g./ 100 ml. of solutizer solution.Samples run with both salt and oil additives contained .05 g. /l'00 ml.of each ad'- diti-ve. The oil used in the sample was an East Texas gasoil having a boiling range between 491.9 and 710.6 R, an aniline pointof l6'7.9 F., and a specific dispersion of 123. The composition of theoil was 12.3% aromatic carbon (one and two ring), 29.6% naphthenecarbon; and 58.1% alkyl carbon.

We claim as our invention:

1. In the process of extracting weak acids nor mally associated. withhydrocarbons from gaso lines containing them and being substantiallyfree from acid-sulfuric acid derivatives with an aqueous alkalinesolution, the improvement comprising extracting said hydrocarbons withsaid aqueous solution containing thoroughly disperseda small amount of amixture of two agents: (1) a water-soluble surface active alkali metalsalt of an acid selected from the group consisting of organic sulfonicacids andsulfate ester acids,

whichacids are free from carboxyl radicals and (2) a mineral oil havinga boiling range between about 400 and about 900 F.

2. In the regenerative process of extracting weak acids normallyassociated with hydrocarbons from gasolines' containing them and beingsubstantially free from acid-sulfuric acid derivatives, with an aqueousalkaline solution to produce a treated hydrocarbon distillate and aspent aqueous solution, wherein said spent solution is regenerated bysteam stripping, the improvement comprising extracting said hydrocarbonswith said aqueous solution containing dissolved not in excess of about1% by weight of a water-soluble surface active alkali metal salt of anacid selected from the group consisting of organic sulfonic acids andsulfate ester acids, which acids are free from carboxyl radicals andradicals susceptible to hydrolysis upon steaming in the presence ofcaustic alkali, having at least 10 carbon atoms and aqueous solutioncontaining dispersed a mineral oil in a concentration not in excess ofabout 2% by weight thereof, said mineral oil having a boiling rangebetween about 400 and about 900 F.

3. The process of claim 2 wherein said mineral oil is continuously addedto said spent solution substantially to maintain said concentration. 4.In the process of sweetening sour gasoline distillates containingmercaptans by extracting them with an aqueous alkaline solutioncontaining a solubility promoter for mercaptans, the improvementcomprising treating gasoline with said aqueous solution containing anaddition thoroughly dispersed a smallamount of a mixture of two agents:(1) a water-soluble surface active alkali metalsalt of an acid selectedfrom the "group consisting of organic sulfonic acids and sulfate esteracids, which acids are fre from carboxyl radicals, and (2') amineral oilhaving a boiling range between about 400 and about 900 F.

5. In the process of extracting weak acids normally associated withhydrocarbons from gasolines containin them, and being substantially freefrom acid-sulfuric acid derivatives, with an aqueous alkaline solution,the improvement comprising extracting said hydrocarbons with saidaqueous solution containing thoroughly dispersed a small amount of amixture of two agents: (1) a water-soluble surface active alkali metalsalt of an alkyl naphthene sulfonic acid, and (2) a mineral oil having aspecific dispersion of below and a boiling range between about 400 andabout 900 F.

6. In the process ofextracting weak acids normally associated withhydrocarbons from gasolines containing them and being substantially freefrom acid-sulfuric acid derivatives, with an aque ou alkaline solution,the improvement c0mprising extracting said hydrocarbons with saidaqueous solution containing thoroughly dispersed a small amount of amixture of two agents: (1) a water-soluble surface active alkali metalsalt of an alkylated hydrocarbon sulfonic acid, and v(2) a mineral oilhaving a boiling range between about 400 and about 900 F.

7. In the process of extracting weak acids normally associated withhydrocarbons from gasolines containing them and being substantially freefrom acid-sulfuric acid derivatives, with an aqueous alkaline solution,the improvement comprising extracting said hydrocarbons with saidaqueous solution containing thoroughly dispersed a small amount of amixture of two agents: (1) a water-soluble surface active alkali metalsalt of an alkylated aromatic sulfonic acid and (2) a mineral oil havinga boiling range be tween about 400 and about 900 F. r

8. In the process of extracting weak acids normally associated withhydrocarbons from gasolines containing them and being substantially freefrom acid-sulfuric acid derivatives, with an aqueous alkaline solution,the improvement comprising extracting said hydrocarbons with saidaqueous solution containing thoroughly dispersed a small amount of amixture of two agents: (1) a water-soluble surface active alkali metalsalt of a petroleum sulfonic acid, and (2) a mineral oil having aboiling range between about 400 and about 900 F.

9. In the process of extracting weak acids normally associated withhydrocarbons from gaso lines containing them and being substantiallyfree from acid-sulfuric acid derivatives, with an aqueous alkalinesolution, the improvement comprising extracting said hydrocarbons withsaid aqueous solution containing dissolved from .001% to 1% by weight ofa water-soluble surface active alkali metal salt of an acid selectedfrom the group consisting of organic sulfonic acids and sulfate esteracids, which acids are free from carboxyl radicals and radicalssusceptible to hydrolysis upon steamin in the presence of caustic alkalihaving at least carbon atoms and a molecular weight below about 1000,and said aqueous solution containing dispersed from .001 to 2% by weightof a mineral oil having a specific dispersion of below 150, a boilingrange between about 400 and about 900 F., and an aniline point aboveabout 122 F.

10. In the regenerative process of sweetening a sour gasoline distillatecontaining mercaptans by extracting it with an aqueous alkaline solutioncontaining alsolubility promoter for meroaptans to produce a treatedhydrocarbon distillate and a spent aqueous solution containing absorbedmercaptains wherein said spent solution is regenerated by steamstripping, the improvement comprising dissolving in said aqueoussolution a small amount of a water-soluble surface active alkali metalsalt of an acid selected from the group consisting of organic sulfonicacids and sulfate ester acids, which acids are free from carboxylradicals and radicals susceptible to hydrolysis upon steaming in thepresence of caustic alkali having at least 10 carbon atoms and amolecular weight below about 1,000, and dispersing in said aqueoussolution a small amount of a parafiinic mineral oil having a boilingrange between about 500 and about 750 F. and not more than aromaticcarbon,

11. A treating solution consisting of an aqueous solution of an alkalimetal hydroxidehaving a normality of at least 2 and containing dissolveda substantial amount of solubility promoter for mercaptans, a smallamount not in excess of about 1% by weight of a water-soluble surfaceactive alkali metal salt of an acid selected from the group consistingof organic sulfonic acids and sulfate ester acids, which acids are freefrom carboxyl radicals, and said solution also containing thoroughlydispersed therein not in excess of about 2% by weight of a mineral oilhaving a boiling range between about 400 and about 900 F.

12. A treating solutionconsisting essentially oi an aqueous solution ofan alkali metal hydroxide having a normality of at least-2 andcontaining dissolved a solubility, promoter for mercaptans, a smallamount not in excess of about 1% by weight of a water-soluble surfaceactive alkali metal salt of an acid selected from the group consistingof organic sulfonic acids and sulfate ester acids, which acids are freefrom carboxyl radiabout 900 F.

cals and radicals susceptible to hydrolysis upon steaming in thepresence of caustic alkali having at least 10 carbon atoms and amolecular weight below about 1000, and said solution also containingthoroughly dispersed therein from .001% to 2% by weight of a mineral oilhaving a boiling range between about 400 and about 900 F. and an anilinepoint above about 122 F.

13 A treating solution consisting essentially of an aqueous solution ofan alkali metal hydroxide having a normality .of at least 2 andcontaining dissolved a substantial amount of a solubility promoter formercaptans, and a small amount not in excess of about 1% by weight of awater-soluble surface active alkali metal salt of an alkyl naphthenesulfonic acid and said solution also containing thoroughly dispersedtherein from .001% to 2% by weight of a parafiinc mineral oil having aboiling range between about 500 and about 750 R, an aniline point aboveabout 122 F., and not.more than 20% aromatic carbon.

14. A treating solution consisting essentially of an aqueous solution ofan alkali metal hydroxide having a normality of at least 2 andcontaining dissolved a substantial amount of a solubility promoter formercaptans, and a small amount not in excess of about 1% by Weight of awater-soluble surface active alkali metal salt of an alklatedhydrocarbon sulfonic acid, and said solution also containing thoroughlydispersed therein not in excess of about 2% by weight of a mineral oilhaving a boiling range between about 400 and about 900 F.

15. A treating solution consisting essentially of an aqueous solution ofan alkali metal hydroxide having a normality of at least 2 andcontaining dissolved a substantial amount of a solubility promoter formercaptans, and a small amount not in excess of about 1% by weight of awater-soluble surface active alkali metal salt of an alkylated aromaticsulfonic acid, and said solution' also containing thoroughly dispersedthercin not in excess of about 2% by Weight of a mineral oil having aboiling range between about 400 and about 900 F.

I 16. A treating solution consisting essentially of an aqueous solutionof an alkali metal hydroxide having a normality of at least 2 andcontaining dissolved a substantial amount of a solubility promoter formercaptans, and a small amount not in excess of about 1% by weight of awater soluble surface active alkali meta1 salt of a petroleum sulfonicacid, and said solution also con taining thoroughly dispersed thereinnot in excess of about 2% by weight of a mineral oil having a boilingrange between about 400 and ORRIS L. DAVIS. ALAN C. NIXON.

